I'm a newbie myself, but I am wondering...was the oak post green when you cut and fit the joints? I also have a few oak posts that have some decent size checking to them, but not as bad as what you describe. They are seasoned now and should not check any further. I wonder if there is a way to slow the drying of green oak to reduce checking? I wonder if anchor seal applied to the exposed end grains would have helped? There must be a way to control checking to some degree. Maybe mills have a technique? I'd love to hear anyone with knowledge on this.
